Electrochemical cells are commonly employed in a variety of applications, such as implantable medical devices (e.g., cardiac pacemakers, cochlear implants, neurostimulators, active drug pumps, etc.). Known electrochemical cells employ a current collector in combination with a body of active material. The current collector may take the form of flattened metal plate (e.g., titanium doped nickel) having an anode or cathode lead integrally coupled thereto. If the electrochemical cell containing the current collector is to be employed in an implantable medical device, it is desirable that the collector occupy a relative small volume to help maximize the cell's power-density. To this end, the current collector may be provided with a plurality (e.g., a grid) of apertures therethrough defining, for example, a lattice of crisscrossed or interwoven portions or veins. This grid of apertures may also promote cohesion between layers of certain active materials, such as silver vanadium oxide (SVO) powder.
Production of electrochemical cells of the type described above may begin with the introduction of an active material into the casting chamber of a press die. The active material may be, for example, an anode-type metal (e.g., lithium) or a cathode-type mix (e.g., SVO powder). Next, a collector chosen from a supply of collectors is inserted into the press die and subsequently pressed onto the active material. During pressing, the active material is compressed and adheres to the bottom side of the collector. After pressing, another layer of active material is introduced into the die and placed under pressure by a flat press to adhere the material to the top side of the collector. Lastly, the collector and active material are removed from the press die and inserted into a casing to complete construction of the electrochemical cell.
As with any process, the above-described cell construction process has certain limitations, many of which relate to the pressing of a current collector onto the active material. Current pressing methods involve manual insertion of a current collector into the press die and subsequent manual pressing. This has occasionally led to the misalignment of a collector relative to the active material and/or an uneven application of pressure over the surface of the collector, possibly causing deformation (e.g., bending, twisting, etc.) of the collector. In addition, the active material is known to extrude through the collector's apertures during the pressing process. This typically results in a reduction in thickness of the active material on the underside of the collector and, consequently, an undesirable asymmetry between active material layer thicknesses. Other difficulties with current cell construction processes are encountered outside of the pressing procedure. For example, collectors are occasionally found in a warped (e.g., a slightly concave, convex, or twisted) condition. As current cell construction processes do not effectively correct for misshapen collectors, the collector may be pressed onto the active material in its warped condition. Again, this may result in a misalignment between the collector and active material layers, especially if the active material is a powdered cathode mix (e.g., SVO powder) capable of sifting through the collector's apertures.
Considering the above, it should be appreciated that it would be desirable to provide method and apparatus for picking, placing, and pressing current collectors that overcomes the disadvantages described above (e.g., alignment errors) and that corrects for misshapen collectors. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.